Ion mobility separation devices that separate and detect ions by ion mobility have characteristics enabling operation without requiring a vacuum pump and even under an atmospheric pressure, and are for this reason widely utilized as on-site measurement devices for environment analysis, explosives detection, illegal drugs detection, chemical agents detection and the like. In the ion mobility separation devices, the technology for highly accurately separating ions generated by an ion source and then detecting the ions with high sensitivity and high throughput is an important issue to be addressed for further expanding applications and reducing false detection.
In Patent Literature 1, there is described a time-of-flight ion mobility separation device and a method whereby ions generated by an ion source are accelerated at a certain timing and are then separated based on the difference in the time of arrival at a detector. The ions can be separated by utilizing the characteristics of various ion species having different ion mobilities, whereby a chemical substance can be identified and quantitated.
In Non Patent Literature 1, there is described an asymmetric field application-type ion mobility separation device. In this method, ions are separated by utilizing a change in ion mobility that is caused upon application of a high electric field of 20 kV/cm or above to the ions. The ion mobility change caused by the high field application differs depending on the ion species. Accordingly, when an asymmetric high frequency field is applied between separation electrodes, a deflection unique to the particular ion species is caused. Thus, it is necessary to apply a compensation field for compensating for the deflection between the electrodes so as to allow the ions to travel straight between the separation electrodes without colliding therewith. By setting the compensation field to a specific value, only a specific ion can be allowed to pass and be detected. In addition, by scanning the compensation field, it becomes possible to acquire a complete spectrum.
In Patent Literature 2, there is described a method for achieving reduced size and increased throughput of the ion mobility separation device described in Non Patent Literature 1 by using a flat-plate insulator member of glass and the like. By using the flat-plate insulator member, manufacturing can be made easier. In this patent literature, it is also described that a gas flow path, separation electrodes, and current detection electrodes are arranged in parallel and given respectively separate parameters so as to simultaneously monitor ions under a plurality of different transmission conditions and achieve high throughput. In addition, a method for enhancing ion separation capability by installing a plurality of current detection electrodes in an ion travel direction is also described.
In Patent Literature 3, a method is described whereby, after asymmetric field application-type ion mobility separation, time-of-flight ion mobility separation is performed. Because asymmetric field application-type ion mobility separation and time-of-flight ion mobility separation have different ion separation characteristics, an improvement in ion separation capability can be obtained compared with when an asymmetric field application-type ion mobility separation device or a time-of-flight ion mobility separation device is used individually.